The objective of the proposed work is to correlate the structure and function of biological membranes at the supramolecular level, and thus to gain deeper insights into how membranes are constructed and how specific membrane components, both enzymatic and structural, are spatially arranged and interact to provide a membrane with its differentiated properties. The approach used is to first identify specific structures in selected membrane systems by means of freeze-fracturing or freeze-etching techniques, then to analyse the components further with a combination of electron microscopic, biochemical, and immunological methods, and finally, to correlate the findings with known or suspected properties of these membranes that can be physiologically tested. The membrane systems presently being used for such studies are: the fluid secreting systems of the trypanasomatid flagellate Leptomonas collosoma and of the alga Vacuolaria virescens, the plasma membrane and cortical vesicles of medaka fish eggs, and photosynthetic membranes of higher plants and bacteria.